In the U.S.A, the primary orthodontic treatment procedure utilizes 'external' forces (i.e., multibanded fixed appliances) to achieve treatment goals. In Europe the removable simple plate and functional appliance are the major appliance modalities. Treatment changes are made with 'internal' forces, attempting to harness the natural forces of the orofacial structures. The proposed research will evaluate the therapeutic value of the function corrector of Frankel. One phase of the project will critically examine, over a five year period, the treatment, retention and post-retention changes with the function corrector and compare the results to multibanded fixed appliance therapy. Achievement of treatment objectives and stability of results will be the primary concern. The experimental group (patients 7 to 9 years old with Class II, Division 1 malocculsions) for whom removable appliance therapy is the most appropriate treatment procedure, will be treated with the function corrector utilizing the case selection criteria of Dr. R. Frankel. One control group will consist of patients treated with extraoral force and multibanded fixed appliances. A second control group will be observed but not treated until the emergence of the permanent dentition. A second phase will statistically evaluate lateral cephalometric radiographs and dental casts (1500 records) of patients treated with the function corrector. These records extend over the treatment, retention, and post-retention stages. A third phase will conduct histological and gross studies of periosteal pull, saggital change and condylar growth (after use of a Frankel Corrector) in eight Saimiri Sciureus monkeys.